1. Field of the Invention
The present invention generally relates to tools, and more specifically, to a driver tool having an elongate handle which embodies at least one permanent efficient high energy magnet on the tool handle for magnetizing the exposed tips of screwdriver bits or other drivers mounted on the handle.
2. Description of Prior Art
It is frequently desirable to magnetize the tips of screwdriver bits and the like to form at least temporary magnetic poles on the tips which attract magnetizable elements. Thus, particularly with precision screwdrivers which tend to be relatively small and are used to drive relatively small screws, it is frequently advantageous to magnetize the screwdriver tips of the driver bits to maintain the screwdriver tip blade within the slot of a head of a screw or a phillips driver within the cross slots formed within the head of the screw adapted to receive the phillips screwdriver tip. By magnetizing the tip of the driver bit, and mating the tip within the associated opening in the head of the screw, the screw remains attached to the bit tip without the need to hold them together. This allows the screw to be guided through a relatively small bore or channel and moved within confined spaces. Sometimes, the magnetized tip of the driver bit is used to retrieve a metal item, such as a screw, washer, nail or the like, from an inaccessible place which would otherwise be difficult to reach with anything but a relatively thin shank of a bit driver. Of course, such attachment of a fastener to the driver bit tip also frees one hand for holding or positioning the work into which the fastener is to be driven.
Devices for magnetizing/demagnetizing tools and small parts are well known. These normally incorporate one or more permanent magnets which create a sufficiently high magnetic field to magnetize at least a portion of a magnetizable element brought into its field. The body can be magnetized by bringing it into a magnetic field. While the magnetic properties of all materials make them respondent in some way to magnetic fields, most materials are diamagnetic or paramagnetic and show almost no response to magnetic fields. However, a magnetizable element made of a ferromagnetic material readily responds to a magnetic field and becomes, at least temporarily, magnetized when placed in such a magnetic field.
Magnetic materials are classified as soft or hard according to the ease of magnetization. Soft materials are used as devices in which change in the magnetization during operation is desirable, sometimes rapidly, as in AC generators and transformers. Most bit drivers are made magnetically soft materials which are not normally magnetized. In order for such bit drivers to exhibit magnetic poles they must be placed in a magnetic filed. Hard materials are used to supply fixed fields either to act alone, as in a magnetic separator, or interact with others, as in loud speakers and instruments.
Most magnetizers/demagnetizers include commercial magnets which are formed of either Alnico or are of the ceramic type. The driver members, on the other hand, are normally made of soft materials which are readily magnetized but more easily lose their magnetization, such as by being drawn over an iron or steel surface, subjected to a demagnetizing influence, such as heavy magnetic fields or other permanent magnetic fields, severe mechanical shock or extreme temperature variations.
One example of a magnetizer/demagnetizer is magnetizer/demagnetizer Model No. 40010, made in Germany by Wiha. This unit is in the form of a box made from plastic and forms two spaced openings defined by three spaced transverse portions. Magnets are placed within one of the transverse portions to provide magnetic fields, in each of the two openings which are directed in substantially opposing directions. Therefore, when a magnetizable tool bit or any magnetizable component is placed within one of the openings, it becomes magnetized and when placed in the other of the openings, it becomes demagnetized. The demagnetizing window is provided progressive steps to decrease the air gap for the demagnetizing field and, therefore, provides different levels of strengths of the demagnetizing field. However, typical magnetic materials that are used with conventional magnetizers/demagnetizers include Alnico and ceramic magnets which typically have energy products equal to approximately 4.5.times.10.sup.6 gauss-oersteds and 2.2.times.10.sup.6 gauss-oersteds, respectively.
Since the field strength B at the pole of the magnet is a product of the unit field strength and the area, and since the force of the magnet (H) is the product of the unit force (are the same unit field strengths) and the length of the magnet, it follows that the energy content or BH product, is proportional to the volume of the magnet. It is for this reason that conventional magnetizers/demagnetizers have required bulky magnets having significant volumes to provide the desired energy content suitable for magnetizing and demagnetizing parts. However, the required volumes have rendered it impossible or impractical to incorporate the magnetizers/demagnetizers on the tools in conjunction with which they are frequently used. Thus, for example, precision screwdrivers, which are relatively small and have relatively small diameter handles could not possibly incorporate sufficient magnetic material to provide desired or required levels of magnetic fields for magnetizing and demagnetizing parts. However, the requirement of using separate magnetizers/demagnetizers units, has rendered their use less practical. Thus, unless a user of a precision screwdriver or any driver tool obtained a separate magnetizer/demagnetizer one would not normally be available for use. Additionally, even if such magnetizer/demagnetizer were available, it would require a separate component which could be misplaced and not available when needed. Of course, there is always the risk that the magnetizer/demagnetizer could become misplaced or lost, rendering the use of the driver tool less useful.
A well known design of a magnetizable driver tool 10 is illustrated in FIG. 1, in which the handle 12 is provided with central axial channel 14 which receives a portion 16a of a driver bit, leaving an external portion 16b exposed which has, at its free end, an operating tip 16c for driving, for example, a fastener. Another operative tip 16d is typically provided at the other end of the bit driver 16 which may be the same as or different than the operative tip 16c. In FIG. 1, the operative tip 16c is a screwdriver tip while the operative tip 16d is a Phillips driver. A chuck 18 may be used to selectively remove the bit driver 16 and reverse its direction to allow use of either one of the two operative tips or to replace the driver with another driver bit. In an effort to magnetize the bit driver 16, and more specifically provide a pole at the operative tip 16c which can attract a magnetizable fastener, there has typically been provided an in-line permanent magnet 20 arranged along the axis A of the tool with poles at 20a and 20b as shown. Such a magnet 20 gives rise to a magnetic field of the type illustrated and designated by the reference numeral 22. However, as will be seen, such field 22 only partially interacts with the bit driver 16, and primarily that portion of the driver 16d closest to the magnet 20. Such magnetic field does not create a very strong magnetic pole at the operative tip 16c. In order to increase the strength of the pole, the size of the magnet 20 has been increased in order to enhance the magnetic field 22. However, this rendered the magnet 20 relatively large in relation to the size of the handle 12 and significantly increased the weight of the tool. Even so, the degree of magnetic field coupling to the bit driver 16, particularly the exposed operative tip 16c, has remained low and, thus, the strength of the magnetic pole created at that end has remained relatively small.